fix(window): the title a program passes to gl_open / gvk_open reaches the window

The runtime opens a game's window before main, titled with the program's name, and
gl_open attached to it without passing its title on (render3d's gvk_open called win_open,
which returns early on Windows and opened a second window on macOS). win_set_title in
cocoa.ll / win32.ll (setTitle: / SetWindowTextW, UTF-8 -> UTF-16; a no-op without a window,
stubbed headless) retitles it from gl_open, and win_open on an open window retitles it on
both platforms.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

changes/window-title.md

@@ -0,0 +1,8 @@
+bump: patch
+type: fix
+A game's window takes the title it asks for. The runtime opens a game's window before `main`,
+titled with the `program` name, and `Gl.open` / render3d's `gl_open` and `gvk_open` attached
+to it without passing their title on, so a `program Valley` that opened "Maroon Lake" showed
+"Valley". `win_set_title` (cocoa.ll `setTitle:`, win32.ll `SetWindowTextW`, UTF-8 to UTF-16)
+now retitles it, and a second `win_open` on macOS retitles the open window instead of making
+another, as it already did on Windows.

packages/ludic.render3d/gpu_vk_draw.ludic

@@ -1411,7 +1411,7 @@ function gvk_open(w: int, h: int, title: string) -> bool {
   gl_w = w
   gl_h = h
   if is_windowed() {
-    win_open(w, h, 1, title)
+    win_open(w, h, 1, title)          # the window exists before main: this retitles it
     win_gl_resize(w, h)
     if gvk_size_buf == null { gvk_size_buf = words(4) }
     win_gl_drawable(gvk_size_buf)

runtime/native/cocoa.ll

@@ -229,7 +229,15 @@ entry:
   store i32 %w, ptr @W_fbw
   store i32 %h, ptr @W_fbh
   store i32 %scale, ptr @W_scale
-
+  ; a window already open (the runtime opens a game's before main) is retitled, not
+  ; opened again - as win32.ll's win_open does
+  %have = load ptr, ptr @W_win
+  %again = icmp ne ptr %have, null
+  br i1 %again, label %retitle, label %make
+retitle:
+  call void @win_set_title(ptr %title)
+  ret void
+make:
   %appcls = call ptr @objc_getClass(ptr @.c_app)
   %sel_sh = call ptr @sel_registerName(ptr @.s_shared)
   %app = call ptr @objc_msgSend(ptr %appcls, ptr %sel_sh)
@@ -1700,6 +1708,31 @@ out:
   ret void
 }
 
+; ---- win_set_title --------------------------------------------------------------------
+; Retitle the window the runtime opened before main: gl_open / gvk_open attach to that window
+; rather than opening one, and the title the program asked for would otherwise be dropped in
+; favour of the program's name. A no-op without a window.
+define void @win_set_title(ptr %title) {
+entry:
+  %win = load ptr, ptr @W_win
+  %nowin = icmp eq ptr %win, null
+  %notitle = icmp eq ptr %title, null
+  %skip = or i1 %nowin, %notitle
+  br i1 %skip, label %out, label %go
+go:
+  %strcls = call ptr @objc_getClass(ptr @.c_str)
+  %sel_utf8 = call ptr @sel_registerName(ptr @.s_utf8)
+  %ns = call ptr (ptr, ptr, ptr) @objc_msgSend(ptr %strcls, ptr %sel_utf8, ptr %title)
+  %none = icmp eq ptr %ns, null
+  br i1 %none, label %out, label %set
+set:
+  %sel_title = call ptr @sel_registerName(ptr @.s_title)
+  %r = call ptr (ptr, ptr, ptr) @objc_msgSend(ptr %win, ptr %sel_title, ptr %ns)
+  br label %out
+out:
+  ret void
+}
+
 ; ---- App.window_hide / App.window_show ------------------------------------------------
 ; The game's window leaves the screen and comes back with its view, layer and GL context
 ; untouched: a launcher steps aside while the game it started runs. The run does not end

runtime/native/gl.ll

@@ -378,6 +378,12 @@ entry:
 }
 ; the drawable's size, for a graphics API that follows the window without a GL context (render3d's
 ; Vulkan resize check); headless there is no window, so 0 x 0. cocoa.ll's real one wins when linked.
+; win_set_title: cocoa.ll's in a windowed build; nothing to retitle headless
+define weak void @win_set_title(ptr %title) {
+entry:
+  ret void
+}
+
 define weak void @win_gl_drawable(ptr %out) {
 entry:
   store i32 0, ptr %out

runtime/native/gl.ludic

@@ -20,6 +20,7 @@ import "gl_api.ludic"
 
 # ---- native glue (cocoa.ll / gl.ll) -------------------------------------------
 extern function win_gl_attach() -> int = "win_gl_attach"
+extern function win_set_title(title: pointer) -> void = "win_set_title"
 extern function win_gl_resize(w: int, h: int) = "win_gl_resize"
 extern function win_gl_swap() = "win_gl_swap"
 extern function win_gl_scale() -> int = "win_gl_scale"
@@ -91,6 +92,10 @@ function gl_open(width: int, height: int, title: pointer) -> bool {
     if win_gl_attach() == 0 {
       win_open(width, height, 1, title)               # a plain program: no window yet
       if win_gl_attach() == 0 { return false }
+    } else {
+      # a game's window was opened before main, titled with the program's name: give it
+      # the title this call asks for
+      win_set_title(title)
     }
     win_gl_resize(width, height)
     gl_scale = win_gl_scale()

runtime/native/gl_win_nowin.ll

@@ -52,3 +52,8 @@ define ptr @win_native_instance() {
 entry:
   ret ptr null
 }
+
+define void @win_set_title(ptr %title) {
+entry:
+  ret void
+}

runtime/native/win32.ll

@@ -50,6 +50,8 @@ declare i64 @DefWindowProcA(ptr, i32, i64, i64)
 declare i32 @ShowWindow(ptr, i32)
 declare i32 @SetForegroundWindow(ptr)
 declare i32 @BringWindowToTop(ptr)
+declare i32 @SetWindowTextW(ptr, ptr)
+declare i32 @MultiByteToWideChar(i32, i32, ptr, i32, ptr, i32)
 declare i32 @PeekMessageA(ptr, ptr, i32, i32, i32)
 declare i64 @DispatchMessageA(ptr)
 declare ptr @GetDC(ptr)
@@ -188,7 +190,11 @@ entry:
   store i32 %scale, ptr @W_scale
   %have = load ptr, ptr @W_hwnd
   %again = icmp ne ptr %have, null
-  br i1 %again, label %out, label %make
+  br i1 %again, label %retitle, label %make
+retitle:
+  ; already open (before main, for a game): take the title this call asks for
+  call void @win_set_title(ptr %title)
+  br label %out
 make:
   ; DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = -4
   %dpi = call i32 @SetProcessDpiAwarenessContext(ptr inttoptr (i64 -4 to ptr))
@@ -268,6 +274,33 @@ out:
   ret void
 }
 
+; ---- win_set_title --------------------------------------------------------------------
+; Retitle the window opened before main (gl_open / gvk_open attach to it rather than opening
+; one, and would otherwise leave the program's name on it). UTF-8 in, UTF-16 to the window.
+; A no-op without a window.
+define void @win_set_title(ptr %title) {
+entry:
+  %h = load ptr, ptr @W_hwnd
+  %nowin = icmp eq ptr %h, null
+  %notitle = icmp eq ptr %title, null
+  %skip = or i1 %nowin, %notitle
+  br i1 %skip, label %out, label %size
+size:
+  %n = call i32 @MultiByteToWideChar(i32 65001, i32 0, ptr %title, i32 -1, ptr null, i32 0)
+  %bad = icmp sle i32 %n, 0
+  br i1 %bad, label %out, label %conv
+conv:
+  %n64 = sext i32 %n to i64
+  %bytes = mul i64 %n64, 2
+  %w = call ptr @malloc(i64 %bytes)
+  %c = call i32 @MultiByteToWideChar(i32 65001, i32 0, ptr %title, i32 -1, ptr %w, i32 %n)
+  %r = call i32 @SetWindowTextW(ptr %h, ptr %w)
+  call void @free(ptr %w)
+  br label %out
+out:
+  ret void
+}
+
 ; ---- App.window_hide / App.window_show ------------------------------------------------
 ; The game's window leaves the screen and comes back with its GL context or Vulkan surface
 ; untouched: a launcher steps aside while the game it started runs. A hidden window is